The invention is based on a process for tightly closing a bore in a work piece made of ductile material.
A process of this kind has already been disclosed (DE-OS 2 301 261), in which the end section of a tube is compressed radially to the tube axis at four opposing points by a multi-part tool in order to close the inner cross section of the tube. This process is relatively simple to use with tubular work pieces, but it fails to function when the cross section to be closed exists as a bore in a solid tool.